C1203 Code: Meaning, Causes, and Symptoms | OBD2 Codes
C1203 – ECM Communication Circuit Malfunction
C1203 Possible Symptoms
Anti-Lock Brake System (ABS) Warning Light ON,Engine Light ON (or Service Engine Soon Warning Light)
C1203 Possible Causes
The wrong ECU or sensor was installed,Skid control ECU (Brake booster with master cylinder assembly)
The circuit is used to send TR(A)C and VSC information from the skid control ECU to the power management control ECU, and hybrid control system information from the power management control ECU to the skid control ECU via the CAN communication system. Identification information sent from other ECUs is stored when shipped from the factory and used as default values.